textproduct: Albany

WHAT HAS CHANGED

Similar to previous forecast, lowered high temperatures for tomorrow given increasing clouds and incoming showers/isolated storms. Also, changed shower/storm coverage to reflect coverage (e.g "isolated", "scattered", etc) instead of probability (e.g "slight chance", "chance", etc) for Friday given diurnal nature to shower/storm coverage.

KEY MESSAGES

1) There is a low to medium chance for isolated to scattered non- severe thunderstorms tomorrow afternoon into the evening hours with a low chance for isolated non-severe thunderstorms mainly near and north of I-90 on Friday.

2) Increasing confidence for a period of above normal temperatures along with higher humidity starting early next week and continuing into the 4th of July holiday. There is a medium chance that high temperatures exceed 90 degrees in valley areas for the middle to end of next week along with daily chances for afternoon thunderstorms.

DISCUSSION

KEY MESSAGE 1...

After a beautiful June day today with seasonable temperatures and plenty of sunshine, we turn our attention to tomorrow as a warm front approaches from the west. Low and mid-level winds become southwesterly tomorrow afternoon as the front lifts eastward out of Central NY, resulting in increasing warm/moisture advection. While there in good consensus that this will support a period of showers and non-severe thunderstorms, especially from north I-90 northward, there are still some timing discrepancies. Some guidance suggests that the incoming warm/moisture advection will be strong enough by 18 - 21 UTC to result in a period of showers and non-severe storms while other guidance indicates continued upper level ridging will maintain overall dry conditions until closer to 00 UTC into Thursday night when a pre-frontal trough along the leading edge of weak height falls and shortwave trough arrives. We continue to side with the mid to late afternoon arrival time for initial showers with chance POPs spreading eastward but delay likely and categorical POPs until Thursday evening when the trough from Great Lakes finally shifts into the Northeast. While dew points trend upwards into the upper 50s to around 60F tomorrow afternoon into the evening, weak lapse rates aloft and increasing cloud coverage will limit instability. MUCAPE values still expected to remain under 500 J/kg with even this meager instability spilling into areas mainly near and west of the Hudson River late afternoon into the evening as the stronger forcing arrives. Despite weak instability, 0-3km shear is noteworthy ranging 30 to 40kts. While this would help result in more organized convection, the overall minimal instability will likely stifle updrafts and thus limit the potential for severe storms. SPC maintains just general thunder for eastern NY and western New England, matching our thinking. Even with limited, if any, storms, expecting a widespread rain event Thurs P.M into Thurs night as PWATs reach near 1 to 1.5". There is a 40 to 70% chance that the 24-hr precipitation across eastern NY and western New England from 12 UTC Thurs to 12 UTC Fri exceeds 0.50 inches. There is only a 15 to 30% chance for over 1 inch of rain indicating flooding issues are unlikely.

The parent shortwave trough moves overhead into Friday with the cold pool supporting slightly steeper lapse rates. This combined with breaks of sun and elevated dew points in the 50s and 60s will likely help generate more appreciable instability compared to Thursday. Still only looking at surface based CAPE values near and above 1000 J/kg with the highest values near and north of I-90 closer to the cold pool. Diurnally driven isolated to scattered showers and thunderstorms look to develop by late morning as we reach our convective temperatures with the activity continuing into the afternoon. Most showers/storms coverage looks focused near and north of I-90 where we show chance POPs with the highest values in the higher terrain areas including the southwest Adirondacks, southern Greens and northern Taconics. Cannot completely rule out an isolated stronger storm given steeper lapse rates, slightly higher instability and decent deep layer shear 45-50kts. SPC maintains just general thunder for our area on Friday so not currently expecting severe weather.

KEY MESSAGE 2...

An amplified ~595dm ridge develops in the Central CONUS early next week which looks to generate a rather impressive heat dome for the Great Plains and Midwest. We remain to the east of the ridge with broad troughing parked over the Canadian Maritimes extending into the Northeast through the early part of the week. However, the ridge finally starts to slide eastward by the middle to end of the week, allowing the heat dome to slide into the Northeast. 850hPa isotherms within the heat dome range 2 to 3 standard deviations above normal per the NAEFS with the latest NBM probabilistic guidance showing a 50 to 65% chances for valley areas to reach or exceed 90 degrees for the middle to end of next week when the very warm air mass finally starts to spill eastward. However, there remains uncertainty regarding just how hot the air mass will be as the trough over the Canadian Maritimes may be stubborn to exit and may erode the incoming heat. In fact, there is a low to medium chance that multiple shortwave riding along the northern periphery of the ridge for the middle to end of next week support a "ridge roller" pattern and lead to daily chances for diurnally driven showers and thunderstorms. Given increasing confidence for daily high temperatures in valley areas near or over 90 degrees for the middle to end of next week combined with increasing humidity, the CPC 8-14 day outlook continues to highlights areas from the Capital District south and west in a "slight risk" (20-40% chance) for extreme heat from July 2 to July 5. This includes the July 4th holiday period where there are many outdoor events schedule so it is important to avoid unnecessary strenuous outdoor activities, drink water even if you are not thirsty, and have a way to stay cool. The slight risk for extreme heat is limited to areas near and south/west of the Capital District given potential for the antecedent trough to erode the heat dome and limit the eastward extent of the heat. That's also why current forecast confidence for heat stands only at medium.

AVIATION /00Z THURSDAY THROUGH MONDAY/

Mainly VFR conditions are expected through the TAF period ending 00Z/Fri. The only caveat could be a bit of patchy ground fog developing later this evening at KGFL and KPSF, however overall probability is quite low due to increasing high clouds. On Thursday, an approaching warm front will bring thickening mid level clouds, with a few showers developing later in the afternoon (mainly after 20Z/Thu) at KGFL, KALB and KPSF. Brief MVFR Vsbys could occur at these locations within any showers.

West/northwest winds 5-10 KT will become light/variable overnight, then trend into the south to southwest at 5-10 KT by late Thursday morning into the afternoon.

ALY WATCHES/WARNINGS/ADVISORIES

CT...None. NY...None. MA...None. VT...None.